About The Eye

Anatomy

Credit: National Eye Institute, National Institutes of Health

How We See

Light enters the eye via the cornea; the amount of light that enters is controlled by the iris, which expands or contracts the pupil in response to the brightness of the scene. The lens then focuses the light into a patterned image on the retina. Cells in the retina called "rods" and "cones" (photoreceptors) convert the light into electrical impulses, which are sent to the brain via the optic nerve. The brain then interprets the impulses and creates what we "see".

Eye Disease: Retinitis Pigmentosa (RP)

Retinitis pigmentosa (RP) is an eye disease which causes damage to the retina. This damage results in a loss of vision. The retina is the layer of tissue at the back of the inside of the eye. The cells in the retina convert light into signals to nerve cells which send signals to the brain. The brain then tells us what we see. The disease is named for the dark deposits which appear in the retina.

RP can be caused by a genetic defect which will cause it to run in families. Early symptoms of the disease often are first experienced in childhood (loss of the ability to see at night or in very low light). Later the disease may lead to blurring of vision, tunnel vision, loss of central vision or loss of the ability to see colors. In many cases, these severe vision problems do not occur until early adulthood. In advanced stages of the disease, RP can lead to a person being able to see only very bright flashes of light. In the worst case, the person may experience total blindness.

Other forms of RP and related diseases include Usher syndrome, Leber's congenital amaurosis, rod-cone disease, and Bardet-Biedl syndrome, among others.